Tubular member extrusion method and tubular member extrusion apparatus

1. Field of the Invention

The present invention relates to a method for fabricating a bent tubular member for use in a hot water line or a fuel line of a motor vehicle or other machines and a tubular member extrusion apparatus.

2. Description of the Related Art

A conventional hose fabrication method for fabricating the type of bent hose described above comprises the following steps. Namely, a hose intermediate is formed by extruding an un-vulcanized rubber. The hose intermediate formed is then cooled and is cut to a predetermined length after a parting agent has been applied thereto. Further, the hose intermediate is manually placed on a metallic mandrel having a bent shape for vulcanization so as to form a hose. Furthermore, the hose is manually removed from the mandrel. In the steps in which the metallic mandrel is used, since the placement of the hose intermediate on the mandrel and removal of the vulcanized hose from the mandrel are manually performed, there is caused a problem that these steps are troublesome.

In addition, as a method for fabricating an extruded product having a bent portion or portions, as is described in Patent Document 1, there has been known a method for fabricating an extruded material having a bent portion or portions. However, even in the event of this technique being applied, there has still been a problem that a three-dimensional complicated bent configuration cannot be dealt with.

Patent Document 1: JP-A-10-263682

The invention has been made with a view to solving the problems inherent in the related art, and an object thereof is to provide a method for fabricating a tubular member having a complicated bent configuration without using a mandrel and an extrusion apparatus for extruding such a tubular member.

The invention has been made with a view to solving at least part of the problems described above, and the invention can be realized as the following forms or application examples.

According to a first aspect of the invention, there is provided a method for forming an extruded tubular member, using an extrusion die that has an extrusion orifice having an inner circumferential surface that is disposed at an opening-side of the extrusion orifice and has a circular section, and a core-side die disposed concentrically with the extrusion orifice, by extruding a tube material through an extrusion passage defined between the inner circumferential surface and an outer circumferential surface of the core-side die, wherein the extruded tubular member is bent by changing contact areas where the tube material contacts the inner circumferential surface and the outer circumferential surface in a circumferential direction so as to set velocities at which the tube material is extruded to different values in the circumferential direction by controlling the position of the core-side die in rotating and axial directions relative to the extrusion orifice.

According to the first aspect of the invention, an extruded tubular member of a straight shape or even an extruded tubular member having a three-dimensional bent configuration with various radii of curvatures can be fabricated by extruding a rubber material continuously while controlling the position of the core-side die in the axial direction or the rotating direction, that is, changing the circumferential contact areas of the rubber material with the opening-side inner circumferential surface and the core-side outer circumferential surface of the extrusion die, whereby superior productivity can be provided.

In addition, a mandrel like the one described in the related art does not have to be inserted into the extruded tubular member for bending, and the work involved becomes simple, the superior productivity being thereby provided.

According to a second aspect of the invention, the core-side die has an inclined plane at a distal end portion of the core-side die which results when a circular cylinder is cut obliquely, whereby the circumferential contact area can be changed by a simple approach.

According to a tubular member extrusion apparatus for forming an extruded tubular member by extruding a tube material, comprising: a hose extrusion unit having an extrusion die having an inner circumferential surface that is disposed at an opening-side of the extrusion orifice and has a circular section and has a circular section and a core-side die disposed concentrically with the extrusion orifice and that is adapted to extrude the tube material through an extrusion passage defined between the inner circumferential surface and an outer circumferential surface of the core-side die; a rubber extrusion unit configured to supply the tube material into the extrusion passage of the hose extrusion unit; and a die position control mechanism configured to change contact areas where the tube material contacts the inner circumferential surface and the outer circumferential surface in a circumferential direction so as to set velocities at which the tube material is extruded to different values in the circumferential direction by controlling the position of the core die in rotating and axial directions relative to the extrusion orifice.

FIG. 1 is an explanatory diagram which explains a hose that is fabricated by a hose (tubular member) extrusion method according to an embodiment of the invention.

FIG. 2 is an explanatory diagram which explains a hose extrusion apparatus for extruding a hose.

FIG. 3 is an explanatory diagram in which the hose extrusion apparatus shown in FIG. 2 is enlarged.

FIG. 4 is an explanatory diagram in which a portion in proximity to an extrusion die is enlarged.

FIG. 5 is a perspective view of the extrusion die.

FIG. 6 is an explanatory diagram which explains the extrusion die.

FIG. 7 is an explanatory diagram which explains a fabrication step performed by the hose extrusion apparatus.

FIG. 8 is an explanatory diagram which explains a step that follows the step in FIG. 7 .

FIG. 9 is an explanatory diagram which explains a step that follows the step in FIG. 8 .

FIG. 10 is an explanatory diagram which explains a step that follows the step in FIG. 9 .

FIG. 11 is an explanatory diagram which explains a step that follows the step in FIG. 10 .

FIG. 12 is an explanatory diagram which explains a step that follows the step in FIG. 11 .

(1) Schematic Configuration of a Hose H Having a Bent Configuration

FIG. 1 is an explanatory diagram which explains a hose that is fabricated by a hose (tubular member) extrusion method according to an embodiment of the invention. A hose H is, for example, a rubber hose that is used in a location where a radiator and an engine is connected and is bent into a three-dimensional configuration to mach a disposition path within an engine compartment. The hose H is fabricated by a hose extrusion apparatus that will be described below.

(2) Hose Fabrication Method

(2)-1 Hose Extrusion Apparatus 10

FIG. 2 is an explanatory diagram which explains a hose extrusion apparatus 10 for extruding a hose H. The hose extrusion apparatus 10 includes a hose extrusion unit 20 , a die position control mechanism 30 adapted to be driven to change a bent configuration of an extruded tubular member HA which is extruded from the hose extrusion unit 20 , and a rubber extrusion unit 40 for supplying a rubber material (a tube material) into the hose extrusion unit 20 .

FIG. 3 is an explanatory diagram in which the hose extrusion unit 20 shown in FIG. 2 is enlarged. The hose extrusion unit 20 includes a die base 22 and an extrusion die 23 which is provided at an end portion of the die base 22 . The die base 22 includes a material supply chamber 22 a into which a rubber material which is supplied from the rubber extrusion unit 40 ( FIG. 2 ) is supplied and a material supply passage 22 b which is connected to the material supply chamber 22 a for sending the rubber material to the extrusion die 23 .

FIG. 4 is an explanatory diagram in which a portion in proximity to the extrusion die 23 is enlarged, and FIG. 5 is a perspective view of the extrusion die 23 . The extrusion die 23 includes an opening-side die 24 and a core-side die 26 . The opening-side die 24 has an extrusion orifice 25 having an opening-side inner circumferential surface 25 a whose inside diameter is set at a predetermined magnification relative to an outside diameter of a hose to be fabricated. An extrusion passage 27 is defined between the opening-side inner circumferential surface 25 a and the core-side die 26 and is connected to the material supply passage 22 b . The core-side die 26 shown in FIG. 3 includes a support base 26 a which penetrates into a through hole 22 c in the die base 22 and a core portion 26 b which is formed integrally at one end of the support base 26 a . The other end of the support base 26 a is connected to the die position control mechanism 30 shown in FIG. 2 , so that the support base 26 a is supported within the through hole 22 c so as to rotate as well as moving backwards and forwards. As is shown in FIGS. 4 and 5 , a distal end of the core portion 26 b is cut at a predetermined angle so as to produce an inclined plane 26 c . In addition, an outer circumference of the core portion 26 b constitutes a core-side outer circumferential surface 26 d which faces the opening-side inner circumferential surface 25 a . The extrusion passage 27 and an extrusion opening 28 , which lies at an end portion of the extrusion passage 27 , are defined between the opening-side inner circumferential surface 25 a and the core-side outer circumferential surface 26 d . Here, as is shown in FIG. 6 , letting a length of the opening-side inner circumferential surface 25 a in an axial direction D be La and a length over which the core-side outer circumferential surface 26 d overlaps the opening-side inner circumferential surface 25 a along the full circumference in the axial direction be an overlapping length L, the overlapping length L can be changed within a range defined as 0≦L<La depending upon an axial position of the core portion 26 b of the core-side die 26 . Namely, a contact area of a rubber material which passes through the extrusion passage 27 with both the opening-side inner circumferential surface 25 a and the core-side outer circumferential surface 26 d changes in a circumferential direction by changing the overlapping length L, whereby a frictional force of the rubber material with both the inner and outer circumferential surfaces is set to differ. Here, the axial length La of the opening-side inner circumferential surface 25 a can be set to 10 mm. As this occurs, the overlapping length L is changed within a range from 0 to 10 mm.

In FIG. 2 , the die position control mechanism 30 includes a lengthwise drive motor 32 and a rotating drive motor 34 which is placed on a support table 33 . The lengthwise drive motor 32 can move the rotating drive motor 34 on the support table 33 in axial directions by driving a drive shaft 32 a . The rotating drive motor 34 is coupled to one end of the core-side die 26 via a coupling 36 at a drive shaft 34 a thereof. Consequently, the position of the core-side die 26 can be controlled in the axial direction as a result of the rotating drive motor 34 on the support table 33 being moved by driving the lengthwise drive motor 32 . In addition, the position of the core-side die 26 can be controlled in the circumferential direction by driving the rotating drive motor 34 .

The rubber extrusion unit 40 includes a cylinder 41 which defines a filling chamber 41 a and a screw 42 which is disposed within the filling chamber 41 a and is adapted to be driven to rotate by a motor, not shown. The rubber extrusion unit 40 connects to the die base 22 of the hose extrusion unit 20 through an injection passage 43 a which is formed in an extrusion head 43 at a distal end of the cylinder 41 . By adopting the configuration of the rubber extrusion unit 40 , when the screw 42 is driven to rotate, a rubber material filled in the cylinder 41 is supplied into the hose extrusion unit 20 through the injection passage 43 a.

(2)-2 Hose H Fabricating Method

Next, a process for fabricating a bent hose H by the hose extrusion apparatus 10 will be described. In the hose extrusion apparatus 10 shown in FIG. 2 , the rubber material within the filling chamber 41 a is supplied into the material supply chamber 22 a of the hose extrusion unit 20 via the injection passage 43 a by the screw 42 of the rubber extrusion unit 40 being driven to rotate. Then, as is shown in FIG. 3 , the rubber material in the material supply chamber 22 a passes through the material supply passage 22 b and further passes through the extrusion passage 27 in the extrusion die 23 , so that an extruded tubular member HA is extruded from the extrusion opening 28 .

In addition, a bending configuration of the hose H is determined by controlling the position of the core portion 26 b of the core-side die 26 by the die position control mechanism 30 . Let's assume that the core-side die 26 is located in a position shown in FIG. 7 as a result of a position control by the lengthwise drive motor 32 and the rotating drive motor 34 of the die position control mechanism 30 shown in FIG. 2 . Namely, the core portion 26 b of the core-side die 26 is set so that the overlapping length L over which the core-side outer circumferential surface 26 d overlaps the opening-side inner circumferential surface 25 a in the axial direction is L 1 (La). In this state, the contact areas of the rubber material with the core-side outer circumferential surface 26 d and the opening-side inner circumferential surface 25 a in the circumferential direction when the rubber material is extruded from the extrusion opening 28 are equal. Therefore, the rubber material receives a uniform frictional force. Consequently, the rubber material is extruded at the same velocity along the circumferential direction, whereby an extruded tubular member HA having a straight shape is formed.

Following this, the core-side 26 is moved in a direction indicated by an arrow d 1 shown in FIG. 8 by driving the lengthwise drive motor 32 of the die position control mechanism 30 so as to decrease the overlapping length L to L 2 . Then, when the rubber material is extruded from the extrusion opening 28 , the contact areas of the rubber material with the core-side outer circumferential surface 26 d and the opening-side inner circumferential surface 25 a differ from each other, whereby the rubber material receives a larger frictional force at a lower portion than an upper portion. Consequently, the rubber material is extruded at different velocities along the circumferential direction, whereby the extruded tubular member HA is formed to be bent in the direction of the slower extruding velocity.

When the core-side die 26 is moved further in the direction indicated by the arrow d 1 as is shown in FIG. 9 so as to decrease the overlapping length L to L 3 , the difference in extruding velocity between in the circumferential positions increases, whereby the extruded tubular member HA is bent at a larger radius of curvature. Then, when the core-side die 26 is moved in a direction indicated by an arrow d 2 and is further rotated through 180° as is shown in FIG. 10 , the extruded tubular member HA becomes straight. Then, when the core-side die 26 is moved in the direction indicated by the arrow d 1 as is shown in FIG. 11 so as to decrease the overlapping length L to L 5 , the extruded tubular member HA is bent upwards as is viewed in the figure. Further, when the core-side die 26 is moved in the direction indicated by the arrow d 1 as is shown in FIG. 12 to decrease the overlapping length L to L 6 , the radius of curvature of the bent configuration of the extruded tubular member HA can be increased. Then, when it is extruded to a predetermined length, the extruded tubular member HA is cut. Then, the extruded tubular member HA so cut is loaded in a vulcanizing pan, not shown, for vulcanization, and a hose having the bent configuration is completed.

(3) Function and Advantage of the Embodiment

The configuration of the embodiment provides the following advantages in addition to the advantage that has been described before.

(3)-1 According to the hose extrusion method of the embodiment, the extruded tubular member H which is straight in shape or even the extruded tubular member having the three-dimensional bent configuration with various radii of curvatures can be fabricated by extruding the rubber material continuously while controlling the position of the core-side die 26 in the axial direction or the rotating direction, that is, changing the circumferential contact areas of the rubber material with the opening-side inner circumferential surface 25 a and the core-side outer circumferential surface 26 d of the extrusion die 23 , whereby superior productivity can be provided.

(3)-2 A mandrel like the one described in the related art does not have to be inserted into the extruded tubular member HA for bending, and the work involved becomes simple, the superior productivity being thereby provided.

(3)-3 The extrusion opening 28 is constant and only the circumferential extruding velocities differ, whereby the resulting extruded tubular material HA has a constant thickness.

The invention is not limited to the embodiment that has been described heretofore and hence can be carried out in various forms without departing from the spirit and scope thereof. For example, the following modification can be adopted.

While the rubber hose has been described as being the tubular member in the aforesaid embodiment, the invention is not limited thereto. The invention can be applied to tubular members that are made of various types of tubular materials including elastomer and metal.